# Deferred Removal Registry

This registry records migration-era code that may become removable after the
physics-facing `StellarModel` and `StellarEquilibriumProblem` APIs have replaced
all legacy construction paths. Nothing listed here is currently approved for
removal, and no listed code was removed during the migration.

## `mean_field::models::Model<...>`

- Location: `libmeanfield/interface/models/specifications.cppm`
- Current status: required compatibility storage
- Current consumers: root-manifest tests and the implementation of
  `mean_field::model::StellarModel`
- Removal gate: migrate remaining direct consumers to the public
  `mean_field::model::StellarModel` type, then move the canonical storage into
  an implementation namespace
- Evidence required before removal: no direct consumers found by repository
  search and the complete specification/type-contract suite passes

## Legacy structure-based `mean_field::models::StellarModel`

- Location: `libmeanfield/interface/models/stellar_model.cppm`
- Current status: retained legacy API, but no longer used by the authoritative
  `StellarEquilibriumProblem` construction path
- Current consumers: direct prepared-operator tests, experiments, and
  heterogeneous runtime-model views. Its polytropic initial-seed method now
  delegates to the physics-facing Lane-Emden seed generator.
- Removal gate: numerical operators consume compiled specification
  contributions directly, initial-seed generation has a physics-facing owner,
  and deformation policies have migrated into the typed model
- Evidence required before removal: legacy-adapter equivalence tests pass for
  all supported formulations and repository search finds no direct consumers

## `PolytropicStructure` as a mass-owning adapter

- Location: `libmeanfield/interface/models/structure/polytropic.cppm`
- Current status: compatibility adapter for remaining legacy API consumers; it
  no longer owns Lane-Emden integration and is not constructed by
  `StellarEquilibriumProblem`
- Potentially obsolete responsibility: ownership of the fixed-total-mass
  target, which now belongs to `FixedTotalMass`
- Removal gate: migrate remaining callers to `seed::LaneEmden` and the typed
  model. Lane-Emden generation is now separate from invariant ownership.
- Evidence required before removal: initial-seed regression tests and
  model-driven equilibrium equivalence tests pass

## Legacy combined prepared operators

- Locations:
  `libmeanfield/interface/operators/prepared_fixed_angular_momentum_stellar_equilibrium.cppm`
  and
  `libmeanfield/interface/operators/prepared_central_density_stellar_equilibrium.cppm`
- Current status: retained as migration-era source references, but removed from
  the build graph and no longer re-exported by the public `mean_field` module
- Physics-facing replacement:
  `PreparedVariadicStellarEquilibriumOperator<Model>`, selected solely by
  `StellarEquilibriumProblem<Model, Discretization>`
- Reactivation gate: migrate the source snapshots to the model-driven manifest
  constructor; they intentionally do not compile against the authoritative API
- Removal gate: delete the source snapshots after the historical comparison
  window closes
- Evidence required before removal: the full variadic residual/Jacobian
  equivalence suite and distributed tests pass without either partition being
  imported by a user translation unit

## Completed: typed equilibrium-problem adapter removal

- Removed the former typed system's `NumericalModelAdapter`, its
  `PolytropicStructure`, and the corresponding legacy model storage.
- The typed problem now owns its compiled surface constraint and constructs the
  prepared operator directly from specification-generated contributions.
- Default radial deformation is compiled at the numerical equilibrium-problem
  boundary rather than being smuggled through a legacy stellar model.

## `StellarEquilibriumSystem` compatibility vocabulary

- Location: `libmeanfield/interface/operators/stellar_equilibrium_system.cppm`
- Current status: source-compatible aliases and factory forwarding to
  `StellarEquilibriumProblem` and `equilibrium::discretize`
- Removal gate: migrate remaining external consumers and provide a documented
  deprecation interval
- Evidence required before removal: repository search finds only the explicit
  compatibility type-contract test

## Root-oriented public aliases and accessors

- Locations:
  `libmeanfield/interface/operators/root_manifest.cppm`,
  `libmeanfield/interface/operators/prepared_stellar_equilibrium.cppm`, and
  `libmeanfield/interface/operators/prepared_central_density_stellar_equilibrium.cppm`
- Current status: retained for source compatibility
- Physics-facing replacements: `EquilibriumSystemManifest`,
  `EquilibriumStateView`, `EquilibriumResidualView`, and
  `StellarEquilibriumProblem::GetManifest()`
- Removal gate: all solver and test consumers use equilibrium-system
  terminology
- Evidence required before removal: repository search finds no uses of the old
  aliases/accessors and all manifest/type-contract tests pass

## Conclusion for this phase

No code examined during this migration is presently truly dead. Each candidate
still has active consumers or carries a compatibility/lifetime responsibility.
The entries above are therefore deferred migration candidates, not deletion
recommendations.